The terminating event of the infective cycle of many viruses is lysis of the host cell with concomitant release of the progeny virus particles. The lysis of cells infected with the coliphage lambda or of induced lambda lysogens occurs synchronously throughout the culture more than thirty minutes after the last known regulatory event of the vegetative cycle. This carefully scheduled lysis was thought for nearly a decade to involve only two lambda genes, S and R, which are the first two genes transcribed on the single lambda late transcriptional unit. Recently, I have discovered a new lysis gene in lambda, mapping adjacent to the R gene; the new gene, designated R., appears to be required for complete destruction of the peptidoglycan. The discovery of the new gene generalizes the problem of how lysis is achieved; apparently, there are at least two genes coding for proteins that attack the peptidoglycan, and both of these functions depend on the function of gene S for access to the periplasm at the proper time. I propose to observe the metabolism of the lysis gene products by gel electrophoretic analysis of labelled proteins synthesized after infection of UV-irradiated cells. The synthesis, stability, and sub-cellular localization of the lysis proteins would be investigated by this method. These data should at least reduce the question of how lysis is achieved and scheduled to molecular terms. In additon, I propose to construct a hybrid lysis operon, in which the lambda lysis gene region is under the control of an inducible promoter; this should answer directly whether other phage genes are involved. Finally, I intend to seek a convenient assay for the S protein, by testing the ability of S function supplied in crude cell-free extracts to alter the permeability properties of spheroplasts and/or whole cell membrane vesicles. The significance of this effort, if successful, lies not only in the resolution of the terminal regulatory event in the lambda growth cycle but also in the answer to the more general quustion - how can protein secretion be temporarily scheduled, independently of the synthesis of the secretory protein.